Split crosslinked polyolefin foam composition and method

ABSTRACT

A process for producing split crosslinked polyolefin sheets comprises producing a crosslinked polyolefin foam sheet having an opposing first surface region and second surface region, and an intermediate region disposed therebetween, wherein the intermediate region is configured to have a gel content lower than an average gel content of the first surface region and the second surface region, and an average cell size larger than an average cell size of the first surface region and the second surface region; and applying a splitting force to the crosslinked foam sheet such that a controlled tear propagation travels through the intermediate region until a first side of the crosslinked polyolefin foam sheet and a second side of the crosslinked polyolefin foam sheet are separated to produce two split polyolefin foam sheets. The split crosslinked polyolefin foam sheets may comprise a skin side comprising a closed cell surface, and a split side comprising an open cell surface having peak heights of about 150 μm to about 550 μm.

PRIORITY CLAIMS

None.

BACKGROUND

The present disclosure relates in general to polyolefin foams, and moreparticularly, to high recovery and splittable large core cell polyolefinfoams and methods of producing the same, wherein the foams comprisenumerous improved structural and mechanical properties both as a singlesheet of foam (prior to splitting) as well as after being split into twosheets of foam, for example.

Conventional methods of producing polyolefin foams include extruding afoamable sheet comprising thermoplastic resins, foaming agents andadditives. Prior to foaming the foamable sheet in an oven at anactivation temperature of the foaming agent, the foamable sheet may becrosslinked via irradiation by passing it through an electron beamirradiator, for example. As is practiced in the art, electron beamirradiators are configured to deliver a sufficient dose of electrons toeach side of the foamable sheet such that the electrons pass all the waythrough the foamable sheet material and exit out the other side whileproviding an even level of crosslinking throughout the foamable sheet.As the electrons pass through the foamable sheet, they impart theirenergy to the material forming crosslinks between the polymer strandsand thereby strengthen the bonds throughout the thickness of thefoamable sheet.

For example, under conventional methods, a foamable sheet may be passedthrough an electron beam irradiator such that a first side is firstexposed with irradiation. The irradiator is configured to deliver asufficient does of electrons such that they travel from the first sideand through the foamable sheet to exit from the opposing, second side,but the electrons lose some energy as they pass through and interactwith the polymer material to crosslink it. This means that the level ofcrosslinking and therefore gel content will be high in a first sidesurface region and progressively diminish through the thickness of thefoamable sheet to a second side surface region, producing a gradient ofcrosslinking. To compensate and create an even level of crosslinking andgel content throughout the whole thickness of the foamable sheet, thesheet is subsequently passed through the electron beam irradiator again,but such that the second side is exposed with the same level ofirradiation, thereby balancing the dose through the thickness of thefoam and achieving an even level of crosslinking throughout including inthe intermediate region of the foamable sheet where the crosslinkinglevels overlap.

A foamable sheet irradiated according to such method, after being foamedin an oven, will have an even degree of crosslinking throughout thethickness of the material, including in both surface regions and anintermediate region therebetween, as well as a uniform cell sizethroughout. Conventionally, it is desirable to have uniform crosslinkingthroughout the foam as well as a uniform cell size, otherwise weaknessesmay be formed within the foam that render it unsuitable for use invarious applications, as well as abnormalities in other properties ofthe foam that may affect its performance.

Patent publication number US20030082364A1, however, discloses a foammaterial with variable crosslinking, wherein one side of the foam isintentionally dosed with a higher irradiation than the other side. Sucha foam will have a first side region having a higher amount ofcrosslinking and smaller cell size, and a second side region having alower amount of crosslinking and larger cell size. The referencediscloses that the greater cross-linking on one side allows the materialto be used in combination with a wider range of materials than ispossible with foamed materials having uniform cross-linking. Thereferences discloses that the foamed material with a varied amount ofcross-linking can have either two distinct levels of cross-linkingacross the material or a gradient of cross-linking across the material,thus allowing control of a range of properties such as heat resistanceduring molding, allowing use of plastics with higher melt temperatures,improved compression set properties in the final product, and improvedhigh temperature performance of the final product. Additionally, thereference discloses it is also possible to cross-link a second timeafter foaming through irradiation or the like. This allows the foamsheet to be produced with lower density without compromising the heatresistance required during the end-use process (such as low-pressuremolding, insert molding, compression molding, etc.).

Although some useful variable cross-linking methods and benefits aredisclosed in reference US20030082364A1, these only include producingfoams having two regions of different crosslinking levels (e.g., highand low sides) and gradients (e.g., progressively high to low or low tohigh crosslinking levels from one side to another). In other words, onlyfoams having two regions with two distinct gel contents, or foams havingonly a gradient of gel contents are envisioned. Notably, each of theseexamples produce a foam having asymmetrical levels of crosslinking, gelcontent and cell size from one side of the foam to the other.

Although these variably crosslinked foams and conventional foams (havinguniform crosslinking) are known in the prior art, there is still astrong need for foams having additional properties not achievable underthose methods alone.

As an example, some end-use applications require a single sheet of foamthat can be split apart in a controlled, even manner, to produce twosheets of foam. When trying to split or tear apart a foam sheet producedby any of the prior art methods, the tear does not propagateconsistently through a core or intermediate region of the foam, butrather surfaces on one side or the other resulting in only a portion orchunk of the foam being pulled apart. In the case of a double-sided foamtape, for example, when an adhered object is removed from a wall orother substrate surface, the entire foam sheet may end up being pulledoff the wall surface, off the object surface, or more often, tornrandomly such that uneven portions of the foam remain on both the walland the object. In a worst-case scenario, portions of the substrate orobject may also be damaged and pulled off.

Furthermore, for foams such as acoustic foams benefiting from an opencell surface structure, conventional methods of converting a singlesheet of foam into two sheets of foam involve skiving the sheet with ablade, rather than physically pulling or tearing it apart, such asdescribed in patent publication number EP0286571B1. The longitudinalcutting of the foam results in an even, open cell surface profile withlittle variation in thickness, for example, and is therefore typicallyfavored in the industry. For example, in EP0286571B1, the referenceteaches skiving a closed cell polyurethane foam panel to form two panelsof identical dimension each having one surface of high density, smallcell structure and each having one surface of low density, large cellstructure, the large cell structure having been skived to create largeopen cells. However, even such skived foam does not always exhibitsufficient acoustic and other properties to satisfy industry demands,including but not limited to adhesive bonding, water retention,anti-slipping and others.

Other known methods of splitting a foam sheet structure involvelaminating each side of the foam to a structural layer and then pullingit apart, as taught for example in patent publication GB738494A. In thatreference, two sheets of pliable non-rubber material were bonded oneither side of a layer of sponge rubber and split longitudinally throughthe thickness of the sponge rubber to produce two sheets of material,each having the pliable non-rubber backing sheet secured to one face ofthe sponge rubber layer, the exposed surface of which had superficialpores of larger dimensions than the pores within the thickness of thesponge rubber layer. However, it is not always desirable to incorporatea laminated backing layer on each pulled apart sheet of foam since thiscan affect the overall properties of the product, limit freedom ofdesign and use, as well as require the additional processing steps andmaterial costs.

Accordingly, there remains a need for an improved foam structure andmethods of producing the same to address the many problems of the priorart. Such foam should have characteristics tailored and appropriate forthe unique specifications of an application where the foam is used.

SUMMARY

This summary is provided to introduce a selection of concepts that arefurther described below in the detailed description. This summary is notintended to identify key or essential features of the claimed subjectmatter, nor is it intended to be used as an aid in limiting the scope ofthe claimed subject matter.

The present disclosure relates to closed cell crosslinked polyolefinfoam sheets, a process for splitting the closed cell crosslinkedpolyolefin sheets, and the split crosslinked polyolefin foam having aclosed cell skin side and an open cell split side.

In one aspect, a closed cell crosslinked polyolefin foam sheet comprisesan opposing first surface region and second surface region, and anintermediate region disposed therebetween, wherein a ratio of a gelcontent of the intermediate region versus an average gel content of thefirst surface region and the second surface region is about 75% or less,and wherein a ratio of the average cell size of the intermediate regionversus an average cell size of the first surface region and the secondsurface region is about 125% or higher.

In another aspect a closed cell crosslinked polyolefin foam sheetcomprises an opposing first surface region and second surface region,and an intermediate region disposed therebetween, wherein theintermediate region is configured to have a gel content lower than anaverage gel content of the first surface region and the second surfaceregion to enable a controlled tear propagation within the intermediateregion when a splitting force is applied to the closed cell crosslinkedpolyolefin foam sheet.

In another aspect a process for producing split crosslinked polyolefinfoam sheets comprises producing a crosslinked polyolefin foam sheethaving an opposing first surface region and second surface region, andan intermediate region disposed therebetween, wherein the intermediateregion is configured to have a gel content lower than an average gelcontent of the first surface region and the second surface region, andan average cell size larger than an average cell size of the firstsurface region and the second surface region; and applying a splittingforce to the crosslinked foam sheet such that a controlled tearpropagation travels through the intermediate region until a first sideof the crosslinked polyolefin foam sheet and a second side of thecrosslinked polyolefin foam sheet are separated to produce two splitpolyolefin foam sheets.

In another aspect, a split crosslinked polyolefin foam sheet comprises askin side comprising a closed cell surface; and a split side comprisingan open cell surface having peak heights of about 150 μm to about 550μm.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a foamable sheet according tothe present disclosure.

FIG. 2 is a schematic perspective view of a foam sheet after foaming thefoamable sheet of FIG. 1.

FIG. 3 is a schematic side cross-sectional view of the foam sheet ofFIG. 2.

FIG. 4 is a schematic side view of the foam sheet of FIGS. 2-3 adheredto a substrate on one side and being split apart.

FIGS. 5A and 5B are schematic side views of the foam sheet of FIGS. 2-3during splitting and after being split apart, respectively.

FIG. 6 is a schematic view of an example production splitting processfor the foam sheet of FIGS. 2-3 according to the present disclosure.

FIGS. 7A-7C are graphs of gel ratio versus foam density for foam sheetsof the present disclosure.

FIGS. 8A-8C are graphs of cell size ratio versus foam density for foamsheets of the present disclosure.

FIGS. 9A-9C are graphs of 50% compression set versus foam density forfoam sheets of the present disclosure.

FIG. 10 is a schematic diagram of the splitting force strength testingapparatus according to the present disclosure.

FIGS. 11A-11C are graphs of splitting force strength versus foam densityfor foam sheets according to the present disclosure.

FIGS. 12A-12C are graphs of T peel strength versus foam density for foamsheets according to the present disclosure.

FIG. 13 is a graph of dent depth recovery for foam sheets according tothe present disclosure.

FIG. 14 is a graph of peak heights versus foam density for split foamsheets according to the present disclosure.

FIG. 15 is a graph of surface roughness versus foam density for splitfoam sheets according to the present disclosure.

FIG. 16A is a graph of the kinetic coefficient of friction versus foamdensity for split foam sheets according to the present disclosure.

FIG. 16B is a graph of the static coefficient of friction versus foamdensity for split foam sheets according to the present disclosure.

FIG. 17 is a graph of average sound reduction (transmittance acoustic)versus foam basis weight for split foam sheets according to the presentdisclosure.

FIG. 18 is a graph of water mass gained (surface water retention) versusfoam density for split foam sheets according to the present disclosure.

FIG. 19 is a graph of peel strength versus test surface type for splitfoam sheets according to the present disclosure.

DETAILED DESCRIPTION

Disclosed herein is an improved polyolefin foam composition and methodof producing the same, wherein the foam comprises numerous improvedstructural and mechanical properties both as a single sheet of foam, aswell as after being split into two sheets of foam, for example. In onenon-limiting example, the foam comprises an intermediate regionconfigured to allow controlled split tear propagation when a thresholdsplitting force is applied, such that a first side and second side ofthe foam split apart from one another in a consistent and even mannerthrough only the intermediate region, and without undesired tears in thefoam outside of that region. Further disclosed is a manufacturingprocess for splitting the foam without the need for skiving.

FIG. 1 is a perspective view of a foamable sheet 10, having a first sideA, a second side B, an intermediate region 12 between sides A and B, aswell as surface region 14A between intermediate region 12 and side A,and surface region 14B between intermediate region 12 and side B.Further represented are the machine direction MD (i.e. lengthdimension), the transverse direction TD (i.e. width dimension), and Zdirection ZD (i.e. thickness dimension) of the foamable sheet 10, inreference to the direction of extrusion of the sheet. The foamable sheetmay be made according to various processes common in the art, includingextrusion, and may include one or more resins, a foaming agent, andsuitable additives.

Polymers or resins suitable for use in the foamable sheet include butare not limited to low density polyethylene (LDPE), linear low densitypolyethylene (LLDPE); medium density polyethylene (MDPE); high densitypolyethylene (HDPE); ethylene vinyl acetate (EVA); polypropylene (PP);ethylene propylene diene monomer (EPDM), thermoplastic olefin (TPO),thermoplastic elastomer (TPE), and rubber. Individual resins may beselected for the foamable sheet, as well as blends of two or moreresins. Suitable foaming agents may include azodicarbonamide (ADCA), forexample.

In contrast with conventional methods for irradiating foamable sheets, anovel controlled depth crosslinking technique is utilized according tothe present disclosure, such that each side A and B of foamable sheet 10is irradiated at a lower energy configured based on the material andeffective thickness of foamable sheet 10. In such case, the electronsentering each side in opposite directions penetrate a thickness of thefoamable sheet that overlaps in the intermediate region 12 before losingenergy and stopping their travel within the foamable sheet, rather thanexiting the other side surface. The slowing down and eventual extinctionof high energy electrons after travelling a certain distance through amaterial may be referred to as the practical range of those electrons.Adjusting the practical range of electrons penetrating the foamablesheet 10 from each side, in turn, such that they travel through aminimal or controlled width overlapping area within the intermediateregion 12 before losing energy, results in a defined intermediate region12 of foamable sheet 10 configured to have a lower degree ofcrosslinking relative to another region of the foamable sheet 10, suchas surface regions 14A and 14B. Further, the position andcharacteristics of the intermediate region 12, including its gelcontent, location and width, can by tightly controlled through adjustingvariables such as material type, effective thickness, voltage potential,dose, line speed, and beam width.

For example, to determine optimal irradiation conditions, electron beamirradiators can be adjusted to change their voltage potential (kV) andcurrent (mA) to affect the amount of dose (Mrads), for example, based onthe effective thickness (ET) of the foamable sheet 10 and its materialtype. ET is calculated by the actual thickness of the foamable sheet(mils), multiplied by the density of the material (g/cm³). Othervariables that may be adjusted according to ordinary skill in the artare line speed (m/min) of the foamable sheet 10 traveling through theelectron beam irradiation machine, and the scan beam width (in) ofelectrons. For example, if line speed is increased, then dose (Mrad) canbe kept constant while the current (mA) must be adjusted accordingly.

With reference to FIG. 2, after the foamable sheet 10 has beenirradiated using the novel controlled depth crosslinking techniquedescribed above, such that intermediate region 12 of foamable sheet 10has a lower degree of crosslinking relative to surface regions 14A and14B, the foamable sheet 10 can then be foamed at or above an activationtemperature of the foaming agent. During the foaming process, foamablesheet 10 will expand in each direction TD, MD and Z to produce foam 10A(e.g., a foamed sheet). Foam 10A will have a resulting gel content inthe intermediate region 12 that is lower than the gel content of regions14A and 14B, and will furthermore have a symmetrical cell sizestructure, with larger cells in the intermediate region 12 andproportionally smaller cells in the surface regions 14A and 14B, asdescribed in more detail below. Importantly, this structure is achievedwithin the single sheet of foam 10A, and does not require lamination orco-extrusion of other foams or other post-processing steps.

FIG. 3 is a cross section of foam 10A of FIG. 2, showing that a largercell structure in intermediate region 12 has resulted after foaming dueto the lower degree of crosslinking (and lower gel content) in thatregion after utilizing the novel controlled depth crosslinking method.Cell formation may be influenced, for example, by the degree ofcrosslinking in the polymers around the foaming agent in the material,thereby restricting the expansion of gas from the foaming agent duringthe foaming process. If the degree of crosslinking is even throughoutthe foamable sheet, as well as the activation of foaming agent duringthe foaming process, then cells will normally expand to reach a similarrestricted size throughout the material in relation to the degree ofcrosslinking. However, when using controlled depth crosslinking asdescribed herein, the gel content and cell size of the intermediateregion 12 of foam 10A can be tightly controlled and configured forcertain specifications versus surface regions 14A and 14B, includingdesired performance properties. These specifications and desiredproperties can not only be controlled for the single sheet of foam 10A,but also with respect to each sheet of foam produced after the foam hasbeen split through controlled tear propagation, which is also enabled bythe present methods.

For example, with respect to the single sheet of foam 10A produced bythe methods described herein, the foam may have a gel ratio configuredto be between about 90% or less, preferably about 75% or less, morepreferably about 50% or less. Gel ratio is calculated by comparing thegel content of the intermediate region 12 to the total average gelcontent of surface regions 14A and 14B, as further described in Example1 of the present disclosure. Alternatively, the gel ratio may be betweenabout 15% to about 90%, preferably between about 15% to about 75%, morepreferably about 15% to about 50%. When lower than about 15%, the foambegins to exhibit blistering due to cell walls breaking down to formlarger blister cells.

The thickness of the intermediate region 12 may also be adjusted to suitthe needs of the foam application, but generally is between about ⅓ toabout ⅔ of the overall foam thickness.

The cell size ratio of the single sheet of foam 10A produced by themethods herein may be calculated as the difference in cell sizes betweenthe intermediate region 12 divided by the total average of the surfaceregions 14A and 14B, as further described in Example 2 of the presentdisclosure. The cell size ratio may be configured to be about 125% orhigher, preferably about 200% to about 400%, more preferably about 250%to about 400%.

Suitable densities of foams produced according to the methods of thepresent disclosure may be between about 1.5 pcf to about 20 pcf,preferably about 1.5 pcf to about 15 pcf, more preferably about 2 pcf toabout 10 pcf.

Further, by configuring the gel ratio and cell size ratio as described,among other features, the foam 10A may be tailored to have desirableproperties suitable for a wide range of applications. For example, foamsproduced according to the methods of the present disclosure may have a50% compression set of under about 10%, preferably about 3% to about10%, more preferably about 4% to about 9%, which is not achievable withstandard irradiated foams.

Foam 10A produced by the methods of the present disclosure may also beconfigured to have improved dent depth recovery versus standard foams,including recovery improvements of about 55% to about 80% versus thestandard foams, as well as improvements of about 35% to about 65% versusstandard foams even after post-crosslinking the foam to improve its heatresistance, as described in more detail with reference to Example 7 ofthe present disclosure. Foam 10A may, for example, have a dent depth ofabout 35% to about 45% of the original thickness at zero hours and about4% to about 6% of the original thickness after 168 hours according totest standard VDA237-101-2. Further, foam 10A may have dent depthrecovery of about 50% to about 55% of the original thickness at zerohours and about 5% to about 10% of the original thickness after 168hours according to test standard VDA237-101-2 after the polyolefin foamsheet has been post-crosslinked to have a gel content in theintermediate region of about 50% or higher.

In another example, the lower degree of crosslinking or gel content inintermediate region 12 may be configured relative to surface regions 14Aand 14B based on the irradiation and foamable sheet 10 conditions toenable a controlled split tear propagation along the intermediate region12 of foam 10A when a threshold splitting force is applied to the foamsheet 10A. The threshold splitting force may be determined based on theneeds of the end-use application, for example, adjusting the degree ofcrosslinking such that it is sufficiently high enough to satisfy theholding strength of a foam tape application, while also beingsufficiently low enough to enable the controlled, even split tearpropagation along and within the bounds of intermediate region 12 andwithout damaging any substrate or object adhered to the foam 10A.

FIG. 4 shows an example of foam sheet 10A adhered on side B to substrateS, while a splitting force SF is represented by a few example vectorspulling on side A either in the Z direction or at some acute anglerelative thereto. After intermediate region 12 has been split apart, newopen cell surfaces 22A and 22B arise, with open cell surface 22A beingopposite closed cell surface A, and open cell surface 22B being oppositeclosed cell surface B.

Further shown is split tear propagation line 16, which stays withinintermediate region 12 in a controlled manner during splitting of foam10A, thereby allowing side A of foam 10A to be evenly peeled away fromside B when a threshold splitting force SF is applied, such as by auser, ultimately producing two separate foam sheets from halves 20A and20B. As described above, the relative degree of crosslinking of surfaceregions 14A and 14B and intermediate region 12 may be configured andtailored to meet the specific needs of an application, for example, toavoid damaging substrate S when an object bound to side A is pulled awayat a threshold splitting force PF. In contrast, a foam produced from afoamable sheet 10 according to the prior art methods, when splitlengthwise (MD) or across (TD) by applying a splitting force in the Zdirection (ZD), for example, will not generate an even split tearpropagation through the material. Rather, the tear 16 will propagaterandomly through the material, outside of intermediate region 12, andmay surface at either side A or B of foam 10A, at which point a chunk ofthe foam may tear off before the whole side has been peeled away. Thisis particularly troublesome for some foam tape applications where it isdesired to evenly split one side of the foam away from the other, ormethods where it is desirable to continuously peel side A away from sideB to produce two foam sheets from one foam sheet.

FIG. 5A shows a similar concept of splitting foam 10A as shown in FIG.4, except wherein neither side of foam 10A is anchored to a substrate,such that foam 10A may be pulled apart by two separate opposingsplitting forces SF to produce two separate foams 20A′ and 20B′. Afterintermediate region 12 has been split apart, new open cell surfaces 22Aand 22B arise, with open cell surface 22A being opposite closed cellsurface A in foam 20A′, and open cell surface 22B being opposite closedcell surface B in foam 20B′.

Splitting force strength of foam 10A is measured as described in Example4 of the present disclosure according to the splitting force strengthtest method, and may be configured to be between about 5 lbf to about 35lbf, preferably about 8 lbf to about 33 lbf, more preferably about 9 lbfto about 30 lbf. The splitting force strength of foams of the presentdisclosure may be significantly reduced in comparison to standard foamshaving comparable densities, the reduction being between about 25% toabout 80%, preferably between about 30% to about 70%, more preferablybetween about 40% to about 60%.

T peel strength of foam 10A is measured as described in Example 5 of thepresent disclosure according to the T peel strength test method and maybe configured to be between about 1 lbf to about 5 lbf, preferably about1.5 lbf to about 4 lbf, more preferably about 1.6 lbf to about 3.1 lbf.The T peel strength of foams of the present disclosure may besignificantly reduced in comparison to standard foams having comparabledensities, the reduction being between about 20% to about 70%,preferably about 30% to about 60%, more preferably about 40% to about50%.

FIG. 6 is a schematic diagram of manufacturing process 100 showing anexample of how the foam 10A according to the present disclosure may becontinuously split. Feed roll F containing foam 10A may be fed to pairsof nip rollers N1, N2 rotating in opposite directions, such as N1 in acounterclockwise and N2 in a clockwise direction as shown. By rotatingin opposing directions, a splitting force SF such as shown in FIG. 5Acan be achieved mechanically from both sides A and B of foam 10A,thereby yielding two sheets of foam 20A′ and 20B′ that can be guidedwith the aid of guide rollers as needed and finally wound up by windingmachines W1 and W2. According to this method, there is no need toutilize or maintain any skiving equipment, since the foam 10A can besplit in half using only the nip rollers N1, N2. Further, the rate atwhich the foam 10A may be split is sufficiently fast to enable it to bepart of an in-line manufacturing process with the foam productionitself.

The controlled split tear propagation enabled by the present disclosureis so effective, it may be tailored to produce two split foams 20A′ and20B′ each having an average gauge of about 30% to about 70% of theoriginal full gauge of the unsplit foam 10A, preferably about 40% toabout 60%, more preferably about 45% to about 55%. Further, split foams20A′ and 20B′ may also each have a mass of about 30% to about 70% of theoriginal full mass of the unsplit foam 10A, preferably about 40% toabout 60%, more preferably about 45% to about 55%. Split foams 20A′ and20B′ may also each have a density of about 75% to about 125% of theoriginal full density of the unsplit foam 10A, preferably about 85% toabout 115%, more preferably about 90% to about 110%, as describedfurther in Example 8 of the present disclosure.

Further, if even, symmetrical halves are desired, the method of thepresent disclosure may yield maximum variances of about 20% for gauge(from and ideal of 50%), about 10% for mass (from an ideal of 50%), andabout 16% for density (from an ideal of 100%), as described further inExample 8 of the present disclosure. The method of the presentdisclosure may also yield maximum average variances of only about 5% forgauge (from and ideal of 50%), about 2% for mass (from an ideal of 50%),and about 6% for density (from an ideal of 100%), as described furtherin Example 8 of the present disclosure.

After splitting, the foams 20A′ and 20B′ may also be configured fornumerous desirable properties. For example, in addition to the gelcontent, cell size and open cell structures that may be created onsurfaces 22A and 22B, foams 20A′ and 20B′ may also comprise advantageousphysical characteristics that provide for additional performanceadvantages as described herein. For example, peak heights of surfaces22A and 22B may range from about 150 μm to about 550 μm, preferably fromabout 200 μm to about 500 μm, and may comprise about a 12 fold increasein peak heights compared with standard foam skin (closed cell surface),and about a 4 fold increase compared with a standard foam skived surface(open cell surface), as described further in Example 9 of the presentdisclosure. Surface roughness (Sa) of surfaces 22A and 22B may rangefrom about 70 μm to about 150 μm, preferably between about 75 μm toabout 140 μm, more preferably between about 80 μm to about 135 um, andmay comprise about a 6 fold increase in surface roughness compared withstandard foam skin (closed cell surface), and about a 1.8 fold increasecompared with a standard foam skived surface (open cell surface), asdescribed further in Example 10 of the present disclosure.

The split foams 20A′ and 20B′ may also be configured such that thecoefficient of friction (COF) between surfaces 22A and 22B rangesbetween about 1.0 lbf to about 4.5 lbf, preferably about 1.5 lbf toabout 4.0 lbf, more preferably about 1.8 lbf to about 3.5 lbf for staticCOF, and for kinetic COF, between about 1.0 lbf to about 4.0 lbf,preferably about 1.5 lbf to about 3.5 lbf, more preferably about 1.5 lbfto about 3.0 lbf. For static COF, this may comprise about a 4.1 foldincrease compared with standard foam skin (closed cell surface), andabout a 3.3 fold increase compared with a standard foam skived surface(open cell surface); and for kinetic COF, may comprise about a 4.4 foldincrease compared with standard foam skin (closed cell surface), andabout a 3.7 fold increase compared with a standard foam skived surface(open cell surface), as described further in Example 11 of the presentdisclosure.

The split foams 20A′ and 20B′ may also be configured such that theaverage sound reduction achieved by surfaces 22A and 22B ranges betweenabout 5 dB to about 25 dB, preferably about 5 dB to about 20 dB, morepreferably about 8 dB to about 17 dB according to the transmittanceacoustic test method described in Example 12 of the present disclosure.Split foams surfaces 22A and 22B according to the present disclosurewill perform better than any standard foam skin surface of comparablebasis weight, and better than any standard foam skived surface for basisweights of about 7 g/sqft or above.

The split foams 20A′ and 20B′ may also be configured such that thesurface water retention of surfaces 22A and 22B ranges between about0.010 grams to about 0.050 grams, preferably about 0.015 grams to about0.045 grams, more preferably about 0.017 grams to about 0.043 gramsaccording to the surface water retention test method described furtherin Example 13 of the present disclosure, and may comprise about a 3.9fold improvement compared with a standard foam skin surface, and about a1.5 fold improvement compared with a standard foam skived surface.

The split foams 20A′ and 20B′ may also exhibit superior adhesiveproperties on surfaces 22A and 22B, having better adhesive anchoragethan a standard foam skived surface, and comparable performance to astandard foam skin surface. For example, the skin peel strength of thesplit foam surface may be about 0.95 N/mm or greater, preferably about1.00 N/mm or greater, more preferably about 1.10 N/mm or greater,according to the adhesive test method and results described further inExample 14 of the present disclosure.

EXPERIMENTAL METHOD

The following formulations of TABLE 1 were used to prepare foamablesheets and foams for the experiments and examples described furtherbelow.

TABLE 1 EVA PE PP Raw Material Type (phr) (phr) (phr) LDPE 100 Lubricant1.2 Sulfer Based AO 0.17 Lubricant 0.5 Catalyst 0.23 Foaming Agent AREVA 100 Lubricant 0.8 Sulfer Based AO 0.17 Catalyst 1.2 Foaming Agent ARLLDPE 20.0 Cataloy PP 25.0 h-PP 35.0 TPE 20.0 crosslinking promoter 3.5Phenol Based AO 1.0 Heat Stabilizer 0.5 Sulfer Based AO 0.5 FoamingAgent AR

Wherein EVA is ethylene-vinyl-acetate, PE is polyethylene, PP ispolypropylene, LDPE is low-density polyethylene, LLDPE is linearlow-density polyethylene, AO is antioxidant, h-PP is a homopolymer ofPP, TPE is a thermoplastic elastomer, and AR denotes “as required” toachieve the target density of the foam as is known in the art.

Foamable sheet samples of were produced based on the formulations ofTABLE 1 and crosslinked according to standard methods to produce controlsamples having even crosslinking throughout, as well as according to thenovel controlled depth crosslinking methods of the present disclosure tohave less crosslinking in their intermediate (i.e. their “core”) regionversus their surface regions and to varying degrees. The foamable sheetswere then foamed at an activation temperature of the foaming agent toproduce foam samples having varying densities for testing according tothe procedures below.

Example 1—Gel Ratio

Gel content of the intermediate region 12 or “core” region, surface A(surface region 14A) and surface B (surface region 14B) was measured foreach irradiated sample of foam produced according to the experimentalmethod above. Using a sharp razor and shims, each foam sample andcontrol was skived into three layers of equal thicknesses, to separateoutside (A-side), intermediate region/core, and outside (B-side)specimens. The crosslinking level of the skived foam samples andcontrols was determined by preparing a 12 mm wide sample with 3 evenslits inside, making four 3 mm wide strips, then cutting at anappropriate length such that the weight of the sample was between 0.047g and 0.053 g. The weighed crosslinked polyolefin foam (A in grams) wasthen immersed in 25 mL of xylene at 120° C. for 24 hours. After 24hours, the content was filtered through a 200-mesh wire mesh and leftsitting inside a fume hood for a minimum of 12 hours. Subsequently, thesample was placed in a 100° C. vacuum oven set at 15 inHG for 4 hoursalong with the wire mesh to vacuum-dry the insolubles on the wire mesh.The dry weight (B in grams) of the insolubles was measured and thecrosslinking level was calculated from the following equation:Crosslinking level (% by weight)=100×(B/A).

A-side and B-side results were averaged to generate an outside gelcontent value, and then the measured gel content value of the coreregion was divided by the averaged outside gel content value to create aratio of core to outside. The results are shown in TABLES 2A, 2B, and 2Cbelow, and corresponding FIGS. 7A, 7B, and 7C, respectively.

TABLE 2A Sample Sample Sample Sample Control Control Control Control EVAFoam 1 2 3 4 1 2 3 4 Density (pcf) 3.3 4.8 5.2 8.6 3.1 4.1 5.6 7.5 Gel(%) A-side 35.1 32.3 27.5 26.1 48.7 41.3 50.6 53.1 Core 16.4 13.7 4.87.5 52.3 39.9 53.9 53.7 B-side 38.1 28.9 30.1 25.1 48.1 36.9 50.4 50.2Ratio 45% 45% 17% 29% 108% 102% 107% 104%

TABLE 2B Sample Sample Control Control Control Control PE Foam 1 2 1 2 34 Density (pcf) 6.9 7.7 1.9 3.9 6.0 12.0 Gel (%) A-side 23 15 48 41.537.6 43.4 Core 10.2 4.6 47 44.4 37.9 44.1 B-side 27.2 23.1 47 43.9 35.742.90 Ratio 40.6% 24.1% 99.4% 104.0% 103.4% 102.2%

TABLE 2C Sample Control Control PP Foam 1 1 2 Density(pcf) 2.6 2.1 4.2Gel (%) A-side 44.4 51.3 41.1 Core 27 47.9 42.4 B-side 41.3 47.1 44.8Ratio 63.0% 97.4% 98.7%

As shown in FIGS. 7A, 7B and 7C, the gel ratio for the control samplesall hovered around 100%, indicating an even level of crosslinking andgel content throughout the samples. However, the gel ratio for thecontrolled depth crosslinking samples were all consistently much lowerthan the controls. These gel % ratios were achieved from about 15% toabout 65% according to the methods of the present disclosure.

Example 2—Cell Size Ratio

Cell sizes of the intermediate region 12 or “core” region, versussurface A (surface region 14A) and surface B (surface region 14B) weremeasured for each irradiated sample of foam produced according to theexperimental method above. A perpendicular cut to the foam was madeusing a sharp razor blade to make sure the sliced surface was pristine.Using a microscope (Keyance 3D microscope VHX-6000) with measurementcapability, cross-sections were observed from each region of foam. Inparticular, five cells were selected from the A-side and five cells fromthe B-side, close to the surface, and then cell sizes were measured inthe z-direction, with the average cell sizes determined. Further, tencells from the core region were selected and measured in thez-direction, and the average determined. Finally, the difference in cellsizes between the core region and surface regions were compared andexpressed as a ratio (core divided by total average of outside regions).The results are shown in TABLES 3A, 3B, and 3C below, and correspondingFIGS. 8A, 8B, and 8C, respectively.

TABLE 3A Sample Sample Sample Sample Control Control Control Control EVAFoam 1 2 3 4 1 2 3 4 Density (pcf) 3.3 4.8 5.2 8.6 3.1 4.1 5.6 7.5 CellSize (μm) Core 1071.9 734.0 1242.9 1077.3 271.9 260.7 295.8 333.3Outside 399.2 328.9 342.5 299.4 261.7 263.1 276.8 275.4 Ratio(Core:Outside) 269% 223% 363% 360% 104% 99% 107% 121%

TABLE 3B Sample Sample Control Control Control Control PE Foam 1 2 1 2 34 Density (pcf) 6.9 7.7 1.9 3.9 6.0 12.0 Cell Size (μm) Core 516.2 618.6354.2 253.1 335.7 307.0 Outside 203.1 239.9 329.4 295.1 331.1 283.0Ratio (Core:Outside) 254% 258% 108% 86% 101% 108%

TABLE 3C Sample Control Control PP Foam 1 1 2 Density (pcf) 2.6 2.1 4.2Cell Size (μm) Core 692.4 598.3 347.3 Outside 309.7 552.5 312.1 Ratio(Core:Outside) 224% 108% 111%

As shown in FIGS. 8A, 8B and 8C, the cell size ratio for the controlsamples all hovered around 100%, indicating an even level of cell sizethroughout the samples. However, the cell size ratios for the controlleddepth crosslinking samples were all consistently much higher than thecontrols, meaning the cell size in the cores was much larger than thecell size in the surface regions. These cell size ratios were achievedfrom about 220% to about 365% according to the methods of the presentdisclosure.

Example 3—50% Compression Set

50% compression set was measured according to ASTM D3575 for eachirradiated sample of foam produced according to the experimental methodabove. The results are shown in TABLES 4A, 4B, and 4C below, andcorresponding FIGS. 9A, 9B, and 9C, respectively.

TABLE 4A Sample Sample Sample Sample Control Control Control Control EVAFoam 1 2 3 4 1 2 3 4 Density (pcf) 3.3 4.8 5.2 8.6 3.1 4.1 5.6 7.5 50%Comp. Set (%) 8.6 3.8 4.1 5.5 19.2 22.1 11.3 14.7 avg 8.6 3.8 4.1 5.519.2 22.1 11.3 14.7

TABLE 4B Sample Sample Control Control Control Control Control PE Foam 12 1 2 3 4 5 Density (pcf) 6.9 7.7 1.9 3.9 6.0 7.0 12.0 50% Comp. Set (%)5.9 7.4 33.4 22.7 15.6 14.3 12.0 avg 5.9 7.4 33.4 22.7 15.6 14.3 12.0

TABLE 4C Sample Sample Sample Control Control PP Foam 1 2 3 1 2 Density(pcf) 2.6 2.8 2.4 2.1 4.2 50% Comp. Set (%) 34.6 32.7 30 34.6 22.72 avg34.6 32.7 30.0 34.6 22.7

As shown in FIGS. 9A, 9B, the 50% compression set was improved (lowered)for all the samples versus the standard control foams. As shown in FIG.9C, the 50% compression set was at least as good or comparable tostandard PP foams, such that performance was not sacrificed.

Further, for each PE and EVA sample (shown in TABLES 4A and 4B), a 50%compression set was calculated for each control sample of a same densitybased on the trend data from FIGS. 9A and 9B respectively and comparedin TABLE 4D below. As shown, 50% compression set was reduced (improved)in each PE and EVA sample compared with the controls of a given density,the % reduction ranging from about 45% to about 75%.

TABLE 4D 50% Comp. Set Sample Control % Comparison (%) (%) ReductionPE - Sample 2 7.4 14.5 49% PE - Sample 1 5.9 15.4 62% EVA - Sample 4 5.513 58% EVA - Sample 3 4.1 15 73% EVA - Sample 2 3.8 15 75% EVA - Sample1 8.6 20 57%

Example 4—Splitting Force Strength

Splitting force strength was measured for each irradiated sample of foamproduced according to the experimental method above. Splitting forcestrength was measured according to the fabricated apparatus shown inFIG. 10 using the splitting force strength test method as follows. Eachfoam sample was corona treated on both sides, then a strong pressuresensitive adhesive was applied to both sides of the foam 10A to convertit into a double-sided foam tape. The foam tape was then cut down to 2inch×1 inch specimens. Making sure the stainless steels of the jig wereclean, the double-sided foam tape 10A was applied on to the smallstainless-steel plate (“S. S. Small Plate” of FIG. 10), on the endwithout the slit and on the side without the indentation. Then, thesmall stainless steel and foam assembly was placed into the 2 inch wideslot of the placement jig, and then the placement jig's hook was placedat the end of the big stainless steel plate (“S.S. Big Plate” of FIG.10). The small plate was pressed firmly onto the big plate and theplacement jig was removed. The small stainless steel and foam assemblywas located 1 inch away from the end of the big plate. The tape wasallowed to cure for 24 hours. Thereafter, the big plate was slid intothe table, and the post under the table was inserted into an instronmachine. The horizontal rod was slid under the small plate, into theindented area, and the vertical rod was allowed to rise up into theslit. The instron grip pinched the tab at the end of the rod and was runin extension mode at 40 inches/min, measuring the splitting force inpounds in both the machine direction (MD) and cross-machine direction(CM) of the foam sheet samples.

The results are shown in TABLES 5A, 5B, and 5C below, and correspondingFIGS. 11A, 11B, and 11C, respectively.

TABLE 5A Sample Sample Sample Sample Control Control Control Control EVAFoam 1 2 3 4 1 2 3 4 Density (pcf) 3.3 4.8 5.2 8.6 3.1  4.1  5.6  7.5Splitting Force MD 11.5 11.2 9.2 33.1 31.3 37.1 37.1 47.2 (lb-f) CM 12.19.4 9.4 25.4 33.1 X X X avg 11.8 10.3 9.3 29.3 32.2 37.1 37.1 47.2

TABLE 5B Sample Sample Control Control Control PE Foam 1 2 1 2 3 Density(pcf) 6.9 7.7 1.93  3.88  5.96 Splitting Force MD 19.1 20.1 13.7 31.738.7 (lb-f) CM 22.8 22.2 14.5 X X avg 21.0 21.2 14.1 31.7 38.7

TABLE 5C Sample Control Control PP Foam 1 1 2 Density (pcf) 2.6 2.1 4.2Splitting Force (lb-f) MD 16.1 19.8 30.7

As shown in FIG. 11A, the force required to split the EVA foam sampleswas much lower than for the control samples regardless of density of thefoam. As shown in FIG. 11B for PE foam samples, the same phenomenon wasobserved, though the lowest density control sample had a slightly lowersplitting force strength than the much higher density sample foams. Withrespect to FIG. 11C, the PP foam sample had a lower splitting forcestrength than the control samples, including the control sample having aslightly lower density. These results show that for a given density offoam, the foam samples prepared according to the controlled depthcrosslinking methods of the present disclosure will consistently haveless splitting force strength than control foams.

Further, for each PP, PE and EVA sample (shown in TABLES 11A-11C), asplitting force strength was calculated for each control sample of asame density based on the trend data from FIGS. 9A and 9B respectively,and compared in TABLE 5D below. As shown, splitting force strength setwas reduced (improved) in each PP, PE and EVA sample compared with thecontrols of a given density, the % reduction ranging from about 25% toabout 80%.

TABLE 5D Splitting Force Sample Control % Strength Comparison (lb-f)(lb-f) Reduction PP - Sample 1 16.1 22.3 28% PE - Sample 1 21 40 48%PE - Sample 2 21.2 40.2 47% EVA - Sample 4 29.3 58 49% EVA - Sample 39.3 37.1 75% EVA - Sample 2 10.3 37.1 72% EVA - Sample 1 11.8 34 65%

Example 5—T Peel Strength

T peel strength was measured for each irradiated sample of foam producedaccording to the experimental method above. The T peel strength testmethod was performed as follows. A 1 inch×6 inch specimen was cut outfrom each foam sample. The samples were partially split by splittingapart approximately 1 inch of the sample material by hand in the case ofthe foam samples produced by controlled depth crosslinking (having largecell size in core region), or by using a razor in the case of thecontrol samples. The two ends from the partial split were pinched by theinstron grips, and the instron was run in extension mode at 10inches/min for 3 inches, measuring the max force to split the foam inhalf in pounds. It was observed that the foam samples produced withcontrolled depth crosslinking continued to split consistently and evenlyover the entire 3 inches, while the control samples ripped unevenlyshortly after the extension started.

The results are shown in TABLES 6A, 6B, and 6C below, and correspondingFIGS. 12A, 12B, and 12C, respectively.

TABLE 6A Sample Sample Sample Sample Control Control Control Control EVAFoam 1 2 3 4 1 2 3 4 Density (pcf) 3.3 4.8 5.2 8.6 3.1 4.1 5.6 7.5 MaxPeel Strength MD 2.1 1.8 1.6 2.8 2.0 3.3 3.6 7.4 10 in/min (lb-f) CM 1.71.5 1.8 3.5 1.7 2.8 3.1 6.8 avg 1.9 1.6 1.7 3.1 1.8 3.0 3.4 7.1

TABLE 6B Sample Sample Control Control Control Control PE Foam 1 2 1 2 34 Density (pcf) 6.9 7.7 1.9 3.9 6.0 12.0 Max Peel Strength MD 2.5 2.40.9 2.5 4.0 12.5 10 in/min (lb-f) CM 2.9 2.2 1.2 2.6 3.8 avg 2.7 2.3 1.02.5 3.9 12.5

TABLE 6C Sample Control Control PP Foam 1 1 2 Density (pcf) 2.6 2.1 4.2Max Peel Strength MD 2.6 3.4 3.8 10 in/min (lb-f) CM 2.8 3.7 3.8 avg 2.73.5 3.8

As shown in FIG. 12A, the T peel strength of the EVA foam samples wasmuch lower than for the control samples, particularly as the density ofthe foam increased. As shown in FIG. 12B for PE foam samples, the samephenomenon was observed, though the lowest density control sample had aslightly lower T peel strength than the much higher density samplefoams. With respect to FIG. 12C, the PP foam sample had a lower T peelstrength than the control samples, including the control sample having aslightly lower density. These results show that for a given density offoam, the foam samples prepared according to the controlled depthcrosslinking methods of the present disclosure will consistently haveless T peel strength than control foams, as well as exhibiting acontrolled tear propagation that the control foams cannot achieve.

Further, for each PP, PE and EVA sample (shown in TABLES 12A-12C), a Tpeel strength was calculated for each control sample of a same densitybased on the trend data from FIGS. 9A and 9B respectively, and comparedin TABLE 6D below. As shown, T peel strength was reduced (improved) ineach PP, PE and EVA sample compared with the controls of a givendensity, the % reduction ranging from about 25% to about 70%.

TABLE 6D T Peel Strength Sample Control % Comparison (lb-f) (lb-f)Reduction PP - Sample 1 2.7 3.6 25% PE - Sample 2 2.3 5.1 54% PE -Sample 1 2.7 6.0 55% EVA - Sample 4 3.1 10 69% EVA - Sample 3 1.7 3.247% EVA - Sample 2 1.6 3.2 50% EVA - Sample 1 1.9 1.9  0%

Example 6—Post-Crosslinking: Heat Resistance

Heat resistance was measured for each irradiated sample of foam producedaccording to the experimental method above. EVA foam samples wereproduced with the controlled depth crosslinking method, andpost-crosslinking (post-XL) samples were produced by subjecting the EVAfoam samples to post-foaming irradiation until their core regions had agel content of at least 50%. These samples were both compared againststandard EVA control foams of comparable density to determine theirability to withstand 21 seconds of extreme heat in a thermal former suchthat the surface temperature of the foams reached around 225 C. Theresults are shown in TABLE 7 below.

TABLE 7 Heat Resistance Test Surface (Surface Temp 225 C. after 21 sec)Degradation? Blistering? EVA Control Foam Yes No EVA Foam Sample Yes YesEVA Foam Sample + Post-XL Yes No

The EVA control foam showed areas of surface degradation, signifying theheat was above the foam's maximum process temperature. The EVA foamsample (having lower gel content core) not only had surface degradation,but severe cases of blistering all over the surface. Blistering wascaused by the large core cells rupturing, combining multiple cells intolarger cells that appear as blisters under the surface. This happened tothe EVA foam sample because the gel in the core area was low and tooweak to be heat stable. However, the post-crosslinked (post-XL) EVA foamsample received an additional dose of irradiation, strengthening thefoam in the core area and increasing gel content there, while preservingthe large cell structure. As a result, the foam surprisingly no longerblistered, but only exhibited surface degradation from the excessiveheat, much like the standard EVA control foam. Accordingly, thecontrolled tear propagation and other performance benefits of the foamsamples may be preserved while also imparting heat resistance featuresto the foam through post-crosslinking.

Example 7—Post-Crosslinking: Dent Depth Recovery

Dent depth recovery was measured for each irradiated sample of foamproduced according to the experimental method above. EVA foam sampleswere produced with the controlled depth crosslinking method, andpost-crosslinking (post-XL) samples were produced by subjecting the EVAfoam samples to post-foaming irradiation until their core regions had agel content of at least 50%. These samples were both compared againststandard EVA control foams of comparable density to determine their dentdepth recovery performance as measured by automotive test standardVDA237-101-2 after 24, 48 and 168 hours. The results are shown in TABLE8A below.

TABLE 8A Dent depth relative to original foam (2 mm) thickness EVA EVAEVA Foam Sample Dent Depth Control Foam Foam Sample (+Post-XL) 1 kg 0 h66% 41% 52% Dent 24 h 18% 13% 12% (mm) 48 h  9%  8%  6% 168 h  6%  6% 5% 2 kg 0 h 90% 38% 50% Dent 24 h 45% 10% 16% (mm) 48 h 28%  6% 13% 168h 15%  4% 10%

FIG. 13 is a graph of the 2 kg dent depth recovery shown in TABLE 8. Ascan be seen, both EVA samples including the post-crosslinked one displaysuperior dent depth recovery to the standard EVA control foam, while thepost-crosslinked sample only suffers a marginal performance reductioncompared with the EVA sample that wasn't post-crosslinked. Accordingly,the mechanical and performance features of the foam samples producedaccording to the method of the present disclosure can largely bepreserved even after the benefits of post-crosslinking are imparted onsuch samples.

Further, the % improvement in dent depth recovery was also individuallycompared between EVA control foam versus the EVA foam sample, and EVAcontrol foam versus EVA Foam Sample (+Post-XL) as shown in TABLE 8Bbelow.

TABLE 8B % Improvement in Dent Depth Recovery Control vs. EVA Controlvs. EVA Sample Sample (+Post-XL) 0 h 57.9% 44.1% 24 h 76.7% 65.2% 48 h80.0% 52.7% 168 h 73.3% 36.7%

As can be seen in TABLE 8B, dent depth recovery of the EVA Sample wasimproved by 55% to about 80% versus the control, while the dent depthrecovery of the EVA Sample that was post-crosslinked was improved byabout 35% to about 65%.

Example 8—Split Foam Gauge, Mass and Density

Foam samples produced according to the experimental method above forcontrolled depth crosslinking were measured for gauge and mass beforeand after splitting them apart using controlled tear propagation downthe intermediate/core region of the foam such as described previouslywith reference to FIGS. 4-6, such that the resulting split foam samplescould be evaluated for their consistency in gauge, mass and calculateddensity. Mass was measured using a calibrated scale, and gauge wasmeasured using a calibrated micrometer.

In the machine direction, ten 4 inch×4 inch specimens were cut from thecenter of the foam sheet sample at 1 inch spacing. The gauge and masswere measured and used to calculate the density of each specimen. Then,each specimen was split using controlled tear propagation into an A-sideand B-side. The gauge and mass of each A-side and B-side split foamsample was then measured and corresponding density was calculated. Sincesome deformation of the foam specimens would occur from the force ofsplitting it, the gauge measurements were taken from non-deformed areasof the split foam sides.

In the cross-machine direction, ten 4 inch×4 inch specimens were cutacross the width of the foam sheet sample at even intervals, and forsheets that were too narrow to obtain ten specimens, then as manyspecimens as possible were collected as allowed by the dimensions of thesheet (7 specimens for the 8 pcf PE foam sample, and 8 specimens for the6.5 pcf EVA foam sample). The first and last specimen were collectedfrom the very edges of the foam sheet. Otherwise, gauge and mass werecollected for the foam before and after splitting, and density wascalculated, according to the same method as described with reference tothe machine direction above.

The gauge, mass and density were then averaged across all the specimensfrom each foam sample, and each value was compared before and aftersplitting the foam. The machine direction (MD) comparison is provided inTABLE 9A below, while the cross-machine (CM) comparison is provided inTABLE 9B below. Each value is expressed as a percentage of the originalunsplit foam sample, such that a perfectly and evenly split foam wouldyield, for each side, an ideal A-side average as well as a B-sideaverage gauge and mass as close as possible to 50% of the originalunsplit sample, as well as a density as close as possible to 100%. Themaximum amount of variance for the samples from the ideal values wasalso determined and is shown in the TABLES 9A, 9B below, as well as theaverage variance of the samples from ideal.

TABLE 9A Gauge (%) Mass (%) Density (%) MD A-side avg B-side Avg A-sideavg B-side Avg A-side avg B-side Avg 2.5 pcf PP 49% 53% 50% 50% 102% 95% 5.2 pcf EVA 51% 51% 51% 49% 99% 97% 8 pcf PE 66% 48% 57% 43% 86% 90%6.5 pcf EVA 53% 53% 49% 51% 93% 96% Total Avg 55% 51% 52% 48% 95% 94%Max Variance 16%  3%  7%  7% 14% 10% Avg Variance  5%  1%  2%  2%  5% 6%

TABLE 9B Gauge (%) Mass (%) Density (%) CM A-side avg B-side Avg A-sideavg B-side Avg A-side avg B-side Avg 2.5 pcf PP 52% 50% 51% 49% 97% 99%5.2 pcf EVA 51% 50% 50% 50% 97% 100%  8 pcf PE 46% 65% 43% 57% 94% 87%6.5 pcf EVA 57% 56% 49% 51% 87% 91% Total Avg 52% 55% 48% 52% 94% 94%Max Variance  7% 15%  7%  7% 13% 13% Max Avg Variance  2%  5%  2%  2% 6%  6%

In some cases, dimensional deformities in the foam samples created someminor inconsistencies in gauge measurements leading to A-side and B-sidetotals which sometimes did not equal 100%. Since density is a functionof gauge and mass, the density calculation likewise was affected in suchcases. However, based on the number of sample specimens studied, thedata nonetheless has a high confidence level.

As can be seen from the TABLES 9A and 9B, the maximum amount of gaugevariance of a split foam specimen was 16%, but on average, was only 5%at most. For mass, the maximum amount of variance of a split foamspecimen was 7%, but on average, was only 2% at most. For density, themaximum amount of variance of a split foam specimen was 14%, but onaverage, was only 6% at most. Therefore, the foam samples produced bythe experimental method had a tear propagation that was highlyconsistent through the core of the foam, leading to A-sides and B-sideshaving very little average variance in gauge, mass and density, makingthis method of the present disclosure highly suitable for massproduction of foam such as described with reference to FIG. 6.

Example 9—Peak Heights

Foam samples produced according to the experimental method above forcontrolled depth crosslinking were measured under a 3D microscope toassess surface peak heights. In particular, split foam samples that weretorn apart using controlled tear propagation down the intermediate/coreregion of the foam such as described previously with reference to FIGS.4-6 were measured for peak heights on the new open cell surface (such as22A and 22B as shown in FIGS. 5A and 5B) as well as measuring the samesurface for standard foam samples that had been skived apart using ablade. Further, peak heights were also measured on the skin side surface(closed cell surface, such as side A and B in FIGS. 5A and 5B) as acontrol. A Keyence 3D microscope VHX-6000 was used to determine peakheights by placing each specimen under the microscope, and using thebuilt-in function, scanning a 5 mm×5 mm area. The base-height wasestablished by taking the average of the entire heights within thescanned area. Local high peaks were selected, and the peak heights weremeasured relative to the established base-height using the microscope'sfunction. The results are shown in TABLES 10A, 10B and 10C below foreach density of foam sample measured, and were further graphed as shownin FIG. 14.

TABLE 10A Skin Foam Density Peak Height Ave Material (pcf) (μm) EVA -Sample 1 3.6 26.1 EVA - Sample 2 7.9 27.8 EVA - Sample 3 5.1 25.7 PE-Sample 1 1.8 38 PE - Sample 2 5.8 23.1 PP - Sample 1 4.3 23.8 PP -Sample 2 5.7 19.4 Total Average 26.3

TABLE 10B Skived Foam Density Peak Height Ave Material (pcf) (μm) EVA -Sample 1 7.5 61.4 EVA - Sample 2 3.6 57.4 PE - Sample 1 5.5 62.5 PE -Sample 2 1.8 123.5 PP - Sample 1 4.1 81.2 PP - Sample 2 6.3 69.6 TotalAverage 75.9

TABLE 10C Split Foam Density Peak Height Ave Material (pcf) (μm) PE -Sample 1 5.5 234.1 PE - Sample 2 7 328.4 EVA - Sample 1 3.6 489.3 EVA -Sample 2 4.7 308.7 EVA - Sample 3 5.1 277.4 EVA- Sample 4 6.8 303.6 PP -Sample 1 2.6 227.8 Total Average 309.9

As can be seen from the results of the measurements and FIG. 14, thesplit foam open cell surfaces of each sample had much higher averagepeak heights than either the skived or the skin surface of comparablefoams. Comparing average peak heights, the split foam surface was about11.8 times higher than skin, and about 4.1 times higher than skived foamsurfaces.

Example 10—Surface Roughness

Foam samples produced according to the experimental method above forcontrolled depth crosslinking were measured under a 3D microscope toassess surface roughness. In particular, split foam samples that weretorn apart using controlled tear propagation down the intermediate/coreregion of the foam such as described previously with reference to FIGS.4-6 were measured for surface roughness on the new open cell surface(such as 22A and 22B as shown in FIGS. 5A and 5B) as well as measuringthe same surface for standard foam samples that had been skived apartusing a blade. Further, surface roughness was also measured on the skinside surface (closed cell surface, such as side A and B in FIGS. 5A and5B) as a control. A Keyence 3D microscope VHX-6000 was used to determinesurface roughness by placing each specimen under the microscope, andusing the built-in function, scanning a 5 mm×5 mm area, with surfaceareas measured by the microscope to calculate a roughness value Sa. Sais the arithmetic average of the surface roughness, and is the extensionof Ra arithmetical mean height of a line. It expresses, as an absolutevalue, the difference in height of each point compared to thearithmetical mean of the surface. The results are shown in TABLES 11A,11B and 11C below for each density of foam sample measured, and werefurther graphed as shown in FIG. 15.

TABLE 11A Skin Foam Density Sa Material (pcf) (μm) EVA - Sample 1 3.618.10 EVA - Sample 2 7.9 18.37 EVA - Sample 3 4.2 23.21 EVA - Sample 44.7 29.08 EVA - Sample 5 5.1 12.72 EVA - Sample 6 3.8 21.01 EVA - Sample7 7.3 20.61 PE - Sample 1 1.8 22.46 PE - Sample 2 3.8 16.40 PE - Sample3 5.8 18.37 PE - Sample 4 5.5 18.10 PE - Sample 5 7.0 16.44 PP - Sample1 3.5 18.79 PP - Sample 2 4.6 17.26 PP - Sample 3 4.3 16.91 PP - Sample4 5.7 16.67 PP - Sample 5 2.0 18.12 PP - Sample 6 2.6 12.40 TotalAverage 18.61

TABLE 11B Skived Foam Density Sa Material (pcf) (μm) EVA - Sample 1 3.735.24 EVA - Sample 2 7.5 39.40 EVA - Sample 3 4.3 62.25 PE - Sample 11.9 76.60 PE - Sample 2 3.9 36.21 PE - Sample 3 5.5 32.88 PP - Sample 13.5 89.84 PP - Sample 2 5.0 63.35 PP - Sample 3 2.0 98.48 PP - Sample 44.1 58.88 PP - Sample 5 6.3 60.28 Total Average 59.40

TABLE 11C Split Foam Density Sa Material (pcf) (μm) EVA - Sample 1 4.783.09 EVA - Sample 2 5.1 85.44 EVA - Sample 3 3.6 97.26 EVA - Sample 46.8 89.66 PE - Sample 1 5.5 114.19 PE - Sample 2 7.0 134.06 PP - Sample1 2.6 124.00 Total Average 103.96

As can be seen from the results of the measurements and FIG. 15, thesplit foam open cell surfaces of each sample had much higher surfaceroughness than either the skived or the skin surface of comparablefoams. Comparing average surface roughness, the split foam surface wasabout 6 times higher than skin, and about 1.8 times higher than skivedfoam surfaces.

Example 11—Coefficient of Friction (COF)

Foam samples produced according to the experimental method above forcontrolled depth crosslinking were assessed according to ASTM D1894 tomeasure their coefficient of friction (COF), both kinetic COF and staticCOF. In particular, split foam samples that were torn apart usingcontrolled tear propagation down the intermediate/core region of thefoam such as described previously with reference to FIGS. 4-6 weremeasured for COF on the new open cell surface against the opposing opencell surface (such as 22A against 22B as shown in FIGS. 5A and 5B) aswell as measuring the same opposing surfaces for standard foam samplesthat had been skived apart using a blade. Further, COF was also measuredon opposing skin side surface (closed cell surface, such as side Aagainst side B in FIGS. 5A and 5B) as a control. The results are shownin TABLES 12A, 12B and 12C below for each density of foam samplemeasured, and were further graphed as shown in FIGS. 16A and 16B.

TABLE 12A Skin-Skin Foam Density Avg Static Avg Kinetic Material (pcf)(lbf) (lbf) EVA - Sample 1 3.6 1.5023 1.3200 EVA - Sample 2 7.9 0.44260.4101 EVA - Sample 3 4.2 0.7409 0.5604 EVA - Sample 4 4.7 0.7950 0.5632EVA - Sample 5 5.1 0.9215 0.7809 EVA - Sample 6 3.8 0.5207 0.4529 EVA -Sample 7 7.3 0.5401 0.4688 PE - Sample 1 1.8 0.4514 0.3360 PE - Sample 23.8 0.4331 0.3108 PE - Sample 3 5.8 0.4336 0.3368 PP - Sample 1 3.50.5485 0.3469 PP - Sample 2 4.6 0.5728 0.3579 PP - Sample 3 4.3 0.55600.5144 PP - Sample 4 5.7 0.5142 0.3418 PE - Sample 5 5.5 0.3848 0.2584PE - Sample 6 7 0.4106 0.2588 PP - Sample 5 2.6 0.5559 0.4232 TotalAverage 0.6073 0.4730

TABLE 12B Skived-Skived Foam Density Avg Static Avg Kinetic Material(pcf) (lbf) (lbf) EVA - Sample 1 3.7 0.9500 0.7445 EVA - Sample 2 7.50.5752 0.4517 EVA - Sample 3 4.3 0.8379 0.6850 PE - Sample 1 1.9 0.96190.7068 PE - Sample 2 3.9 0.6826 0.5189 PE - Sample 3 5.5 0.5486 0.4113PP - Sample 1 3.5 0.8613 0.6047 PP - Sample 2 5.0 0.6034 0.3999 PP -Sample 3 4.1 0.9460 0.7007 PP - Sample 4 6.3 0.6187 0.4156 Total Average0.7585 0.5639

TABLE 12C Split-Split Foam Density Avg Static Avg Kinetic Material (pcf)(lbf) (lbf) EVA - Sample 1 4.7 3.4905 3.0201 EVA - Sample 2 5.1 3.40312.8820 EVA - Sample 3 3.6 2.4210 2.0361 EVA - Sample 4 6.8 1.8622 1.6941PE - Sample 1 5.5 1.9382 1.6119 PE - Sample 2 7 1.8896 1.5659 PP -Sample 1 2.6 2.2686 1.6443 Total Average 2.4676 2.0649

As can be seen from the results of the measurements and FIGS. 16A and16B, the split foam open cell surfaces of each sample had a much higherCOF, both static and kinetic, than either the skived or the skinsurfaces of comparable foams. Comparing average static COF, the splitfoam surface was about 4.1 times higher than skin, and about 3.3 timeshigher than skived foam surfaces. Comparing average kinetic COF, thesplit foam surface was about 4.4 times higher than skin, and about 3.7times higher than skived foam surfaces.

Example 12—Transmittance Acoustic

Foam samples produced according to the experimental method above forcontrolled depth crosslinking were assessed for their transmittanceacoustic properties to determine the average sound reduction achieved bythe foam. In particular, split foam samples that were torn apart usingcontrolled tear propagation down the intermediate/core region of thefoam such as described previously with reference to FIGS. 4-6 weremeasured for average sound reduction across the new open cell surface(such as 22A or 22B as shown in FIGS. 5A and 5B) as well as measuringthe same for standard foam samples that had been skived apart using ablade. Further, average sound reduction was also measured on skin sidesurfaces (closed cell surface, such as side A or side B in FIGS. 5A and5B) as a control.

The transmittance acoustic test method was performed as follows. Two4-inch-long×12 inch diameter PVC pipes were prepared. One end of bothpipes with closed with 1-inch thick wood pieces. A ¾-inch diameter holewas drilled in the center of one of the wood pieces. The pipe withoutthe drilled hole was placed on the table, wood end down. A bluetoothspeaker was placed in the center of the first pipe, facing up. A12-inch×12-inch foam specimen was placed on the first PVC pipe openingwith the tested surface facing the speaker. The second PVC pipe with thedrilled hole was used to sandwich the specimen, with wood facing up. Adecibel meter was inserted through the hole on top, approximately 3inches above the foam specimen. A tone generator software applicationwas used to play a tone ranging from 1000 Hz to 20,000 Hz at 1000 Hzintervals, and the resulting decibels passing through the foam specimenwere recorded, making sure the volume was not too loud to avoid maxingout the decibel meter's functional range. The process was then repeatedwithout the foam specimen to generate the baseline control measurement.Once data was collected, a best fit linear line was generated throughthe data to find the equation. Using the equation, the dB at 1000 Hz and20000 Hz was calculated, and then the specimen values were subtractedfrom the baseline values to generate the sound reduction value. Then,the average sound reduction value was calculated to generate one valueto describe the level of sound reduction from the specimen tested. Theaverage sound reduction value was then graphed relative to thecalculated basis weight of each foam specimen.

The average sound reduction results are shown in TABLES 13A, 13B and 13Cbelow for each basis weight of foam sample measured and were furthergraphed as shown in FIG. 17.

TABLE 13A Skin Basis Weight Ave dB Material (g/sqft) Reduction PE -Sample 1 114.5 28.1 EVA - Sample 1 5.9 8.0 EVA - Sample 2 7.1 7.4 EVA -Sample 3 19.1 13.6 EVA - Sample 4 19.4 15.3 EVA - Sample 5 30.8 15.2EVA - Sample 6 42.7 20.5 PE - Sample 2 7.0 7.6 PE - Sample 3 14.7 12.4PE - Sample 4 22.1 15.4 PE - Sample 5 27.8 19.8 PE - Sample 6 29.8 16.3PE - Sample 7 43.6 22.3 PE - Sample 8 58.6 25.6 PP - Sample 1 18.6 14.0PP - Sample 2 19.0 11.7

TABLE 13B Skived Basis Weight Ave dB Material (g/sqft) Reduction EVA -Sample 1 17.1 15.29 EVA - Sample 2 25.8 16.39 PE - Sample 1 5.0 7.57PE - Sample 2 6.5 6.83 PE - Sample 3 8.1 13.75 PE - Sample 4 15.3 13.49PE - Sample 5 5.6 8.93 PE - Sample 6 10.1 12.71 EVA - Sample 3 8.3 12.68EVA - Sample 4 4.6 9.35 PP - Sample 1 4.0 8.43 PP - Sample 2 9.4 11.48PP - Sample 3 2.9 7.98 PP - Sample 4 4.8 10.01 PP - Sample 5 13.4 11.49PP - Sample 6 7.0 7.69 PP - Sample 7 7.3 14.5 PP - Sample 8 11.6 12.32

TABLE 13C Split Basis Weight Ave dB Material (g/sqft) Reduction PE -Sample 1 14.3 15.2 PE - Sample 2 14.5 16.8 EVA - Sample 1 7.0 9.4 EVA -Sample 2 10.7 13.2 EVA - Sample 3 5.9 9.4 EVA - Sample 4 7.8 12.0 PP -Sample 1 5.2 8.4

As can be seen from the results of the measurements and FIG. 17, thesplit foam open cell surface samples had superior average soundreduction performance compared with standard skin surfaces of foam forall basis weights of foam. In comparison to skived standard foam, thesplit foam surface had superior average sound reduction performance forbasis weights of foam at about 7 g/sqft or above.

Example 13—Surface Water Retention

Foam samples produced according to the experimental method above forcontrolled depth crosslinking were assessed for their surface waterretention properties. In particular, split foam samples that were tornapart using controlled tear propagation down the intermediate/coreregion of the foam such as described previously with reference to FIGS.4-6 were measured for surface water retention properties on the new opencell surfaces (such as 22A or 22B as shown in FIGS. 5A and 5B) as wellas measuring the same for standard foam samples that had been skivedapart using a blade. Further, surface water retention was also measuredon skin side surfaces (closed cell surface, such as side A or side B inFIGS. 5A and 5B) as a control.

The surface water retention test method was performed as follows.4-inch×4-inch foam specimens and a shallow vat of water were prepared.Each specimen was dry weighed, then the specimen's side of interest wasplaced onto the water so it floated. The specimens were allowed to floatfor 45 seconds. During that time, forceps were used to glide eachspecimen over the surface of the water to make sure any trapped airunder the specimen escaped while making sure no water got on the dryside. After 45 seconds, the specimen was picked up from the water andplaced on a scale, dry side down, to weigh the new mass including anywater that was retained by the specimen. The before and after masseswere compared to calculate the amount of water retained on the surfaceof each specimen.

The average surface water retention results are shown in TABLES 14A, 14Band 14C below for each density of foam sample measured and were furthergraphed as shown in FIG. 18.

TABLE 14A Skin Foam Density Water mass gained Material (pcf) (g) EVA -Sample 1 3.6 0.002 EVA - Sample 2 7.9 0.001 EVA - Sample 3 4.2 0.001EVA - Sample 4 4.7 0.001 EVA - Sample 5 5.1 0.003 EVA - Sample 6 3.80.000 EVA - Sample 7 7.3 0.001 PE - Sample 1 1.8 0.014 PE - Sample 2 3.80.009 PE - Sample 3 5.8 0.013 PE - Sample 4 7.0 0.016 PE - Sample 5 5.50.015 PP - Sample 1 3.5 0.013 PP - Sample 2 4.6 0.009 PP - Sample 3 4.30.004 PP - Sample 4 5.7 0.011 Total Average 0.007

TABLE 14B Skived Foam Density Water mass gained Material (pcf) (g) EVA -Sample 1 3.7 0.019 EVA - Sample 2 7.5 0.014 EVA - Sample 3 4.3 0.010PE - Sample 1 1.9 0.021 PE - Sample 2 3.9 0.021 PE - Sample 3 5.5 0.019PP - Sample 1 3.5 0.023 PP - Sample 2 5.0 0.024 PP - Sample 3 4.1 0.021PP - Sample 4 6.3 0.015 Total Average 0.019

TABLE 14C Split Foam Density Water mass gained Material (pcf) (g) EVA -Sample 1 4.7 0.028 EVA - Sample 2 5.1 0.036 EVA - Sample 3 3.6 0.026EVA - Sample 4 6.8 0.043 PE - Sample 1 7.0 0.017 PP - Sample 1 5.2 0.018Total Average 0.028

As can be seen from the results of the measurements and FIG. 18, thesplit foam retained more water on its surface than either the standardskin or skived foam surfaces. This result is interesting in part becauseeven a skived foam will present an open cell surface, however, theparticular surface characteristics of the split foam open cell surfacemade it superior at retaining water, potentially due to the increase inpeak heights and surface roughness as described with respect to previousexamples. Comparing the total average water retention, the split foamsurface retained about 3.9 times more water than the skin surfaces, andabout 1.5 times more water than the skived foam surfaces.

Example 14—Adhesive Test

Foam samples produced according to the experimental method above forcontrolled depth crosslinking were assessed for their adhesiveproperties. In particular, split foam samples that were torn apart usingcontrolled tear propagation down the intermediate/core region of thefoam such as described previously with reference to FIGS. 4-6 weremeasured for adhesive properties on the new open cell surfaces (such as22A or 22B as shown in FIGS. 5A and 5B) as well as measuring the samefor standard foam samples that had been skived apart using a blade.Further, adhesive properties were also measured on skin side surfaces(closed cell surface, such as side A or side B in FIGS. 5A and 5B) as acontrol.

The adhesive test method was performed as follows. Across the width ofthe foam samples, 3 specimens were cut in the MD direction, 350 mm×50mm. Both sides were then corona treated. Samples with a density lowerthan 3.2 pcf did not need to be treated. Samples with densities greaterthan 12.5 pcf were not tested. A pressure sensitive double-sided tapewas prepared using a Coatema coating machine with KS900 as the releaseliner. 65 g/m2 of Collano T2 1434 was applied at 160° C. The foamspecimen was coated on both sides with the prepared double-sided tapewhile avoiding trapping any air. The adhesive was rolled down twice witha 5 kg roller and a uniform speed of 600 mm/min. The specimens were diecut to 300 mm×25 mm. Release liner was removed on one side and a MYLARPET film was placed, 0.019 mm thick, and then rolled twice with a rolleras above. A plane chromium-nickel plate (50 mm×210 mm) was cleaned with600 grit paper (in length direction only) and any shavings, grease, etc.were removed with a lint free paper soaked in benzene. About 11 cm ofthe other release liner was removed from the specimen and placed so theopened adhesive side was on the cleaned metal plate. Starting with theedge of the specimen at the cleaned edge of the metal plate, a rollerwas used to roll it down four times with a roller as above. Then, thespecimen set-ups were allowed to sit for 24 hours. Subsequently, a loadcell was installed in a tensile tester, distance of the grips to at 170mm. With specimens of high density, peel was initiated with a jerkymovement by hand. The free end of the metal plate was installed in thegrip without the load cell, and the loose end of the specimen installedin the grip which had the load cell. Peel strength was tested at a rateof 300 mm/min and recorded in N/mm while observing the location of thepeel in the sample specimen.

The adhesive test results are shown in TABLE 15 below for each foamsample measured and were further graphed as shown in FIG. 19.

TABLE 15 Type of foam 4.5 pcf EVA - 4.0 pcf EVA - 4.0 pcf EVA - 4.5 pcfEVA - split foam control foam control foam split foam Surface testedSkin Side Skin Side Skived Side Split Side Skin peel strength, 1.0701.380 0.920 1.120 MD (N/mm) Failure mode Foam Tear Foam Tear AdhesiveFoam Foam Tear Failure

Regarding the failure mode, foam tear referred to a situation where thefoam itself tore, whereas adhesive foam failure referred to a situationwhere the foam-adhesive tape interface failed, which is a sign that theadhesive is not getting a good anchorage to the foam. These test resultsshow that the adhesive did not anchor to the skived surface very well,whereas the split foam split side resulted in a foam tear, suggestingstrong adhesive anchorage. Further, the split open surface showed aboutthe same performance as the skin side surfaces, though superior to theskived surface. Accordingly, the split foam surface according to themethods of the present disclosure performs well for adhesive tapeapplications.

While the invention has been described with reference to an exemplaryembodiment(s), it will be understood by those skilled in the art thatvarious changes may be made, and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment(s) disclosed, but that theinvention will include all embodiments falling within the scope of theappended claims.

1. A process for producing split crosslinked polyolefin foam sheets,comprising: producing a crosslinked polyolefin foam sheet having anopposing first surface region and second surface region, and anintermediate region disposed therebetween, wherein the intermediateregion is configured to have a gel content lower than an average gelcontent of the first surface region and the second surface region, andan average cell size larger than an average cell size of the firstsurface region and the second surface region; and applying a splittingforce to the crosslinked foam sheet such that a controlled tearpropagation travels through the intermediate region until a first sideof the crosslinked polyolefin foam sheet and a second side of thecrosslinked polyolefin foam sheet are separated to produce two splitpolyolefin foam sheets.
 2. The process of claim 1, wherein each of thetwo split polyolefin foam sheets produced have an average gauge of about40% to about 60% of an original gauge of the crosslinked polyolefin foamsheet.
 3. The process of claim 1, wherein each of the two splitpolyolefin foam sheets produced have an average gauge of about 45% toabout 65% of an original gauge of the crosslinked polyolefin foam sheet.4. The process of claim 1, wherein each of the two split polyolefin foamsheets produced have a mass of about 40% to about 60% of an originalmass of the crosslinked polyolefin foam sheet.
 5. The process of claim1, wherein each of the two split polyolefin foam sheets produced have amass of about 45% to about 55% of an original mass of the crosslinkedpolyolefin foam sheet.
 6. The process of claim 1, wherein each of thetwo split polyolefin foam sheets produced have a density of about 85% toabout 115% of an original density of the crosslinked polyolefin foamsheet.
 7. The process of claim 1, wherein each of the two splitpolyolefin foam sheets produced have a density of about 90% to about110% of an original density of the crosslinked polyolefin foam sheet. 8.The process of claim 1, wherein each of the two split polyolefin foamsheets produced have a maximum average gauge variance of about 5% froman ideal 50%.
 9. The process of claim 1, wherein each of the two splitpolyolefin foam sheets produced have a maximum average mass variance ofabout 2% from an ideal 50%.
 10. The process of claim 1, wherein each ofthe two split polyolefin foam sheets produced have a maximum averagedensity variance of about 6% from an ideal 100%.
 11. A split crosslinkedpolyolefin foam sheet comprising: a skin side comprising a closed cellsurface; and a split side comprising an open cell surface having peakheights of about 150 μm to about 550 μm.
 12. The split crosslinkedpolyolefin foam sheet of claim 11, further comprising peak heights ofabout 200 μm to about 500 μm.
 13. The split crosslinked polyolefin foamsheet of claim 11, wherein the open cell surface further comprises asurface roughness of about 70 μm to about 150 μm.
 14. The splitcrosslinked polyolefin foam sheet of claim 11, wherein the open cellsurface further comprises a surface roughness of about 80 μm to about135 μm.
 15. The split crosslinked polyolefin foam sheet of claim 11,wherein the open cell surface further comprises a static coefficient offriction of about 1.0 lbf to about 4.5 lbf when tested against the sameopen cell surface of another split polyolefin foam according to ASTMD1894.
 16. The split crosslinked polyolefin foam sheet of claim 11,wherein the open cell surface further comprises a static coefficient offriction of about 1.8 lbf to about 3.5 lbf when tested against the sameopen cell surface of another split polyolefin foam according to ASTMD1894.
 17. The split crosslinked polyolefin foam sheet of claim 11,wherein the open cell surface further comprises an average soundreduction of about 5 dB to about 20 dB according to the transmittanceacoustic test method.
 18. The split crosslinked polyolefin foam sheet ofclaim 11, wherein the open cell surface further comprises an averagesound reduction of about 8 dB to about 17 dB according to thetransmittance acoustic test method.
 19. The split crosslinked polyolefinfoam sheet of claim 11, wherein the open cell surface further comprisesa surface water retention of about 0.010 grams to about 0.050 gramsaccording to the surface water retention test method.
 20. The splitcrosslinked polyolefin foam sheet of claim 11, wherein the open cellsurface further comprises a surface water retention of about 0.017 gramsto about 0.043 grams according to the surface water retention testmethod.
 21. The split crosslinked polyolefin foam sheet of claim 11,wherein the open cell surface further comprises a skin peel strength ofabout 0.95 N/mm or greater according to the adhesive test method.